The objective of this proposal is two-fold. One is to collect ultrastructural, biochemical and serological data on microorganisms from the dentogingival area in order to create a data base for the development of an identification scheme for the dentogingival flora. The other is to use some of these bacterial species as antigen sources for the estimation of antibody titers to these microorganisms in selected subjects. In characterizing new isolates, special emphasis will be placed on gram-negative anaerobic rods which morphologically or biochemically do not resemble bacterial species currently listed in the literature, but which appear routinely in bacterial samples from advanced periodontal lesions. Antibody titers to selected microorganisms will be estimated by a fluorescent antibody technique as well as additional, more sensitive methods such as the enzyme-linked immunosorbent assay. The information gained should speed up the development of laboratory tests for improved diagnosis and mamagement of periodontal disease.